The present invention relates to a motor-vehicle door latch. More particularly this invention concerns a power-closing bolt for such a latch.
A motor vehicle door is normally provided on its outer edge opposite its hinged edge with a latch having a fork engage able around a bolt projecting from a door post. The fork can retain the bolt to hold the door closed, and can pivot to release the bolt and allow the door to be opened. On closing the fork is automatically latched the door in the door opening against an annular seal typically carried on the vehicle body.
In today""s vehicles it is important that the door be as tightly closed as possible, in order to reduce drafts and noise. Thus the door should, in the closed position, exert the maximum possible compression on the door seal. This effect is most simply achieved by only letting the latch engage in its end position when the door is forcibly closed, requiring the user to pull or push it solidly to.
Better vehicles incorporate a power-closing system which, once the fork has latched around the bolt, displaces the bolt inward through a short extra stroke that ensures that the door will be tightly closed. The system can also move the bolt outward through its stroke when one of the latches is initially actuated to open the door. In this manner the user is not burdened with having to close a door very tightly, or deal with opening a very tightly closed door. In practice such a system allows a door to be pulled much more tightly closed than could normally be expected by a standard system. These arrangements are also usable on the trunk door as they allow the user to merely push the door to and thereafter it will fully close by its own automatic operation.
Such power closing systems work various ways. In U.S. patent application Ser. No. 09/338,036 filed Jun. 22, 1999, U.S. Pat. Nos. 4,775,178 and 4,842,313, European patent 0,467,057 of U. Koster, and German patent document 4,210,893 published 7 Oct. 1993 for P. Szablewski the bolt is mounted slightly eccentrically on a rotary mount that is driven by an electric motor through a step-down transmission. Pivoting the bolt through 180xc2x0 moves it through a distance equal to twice the eccentric offset of the bolt from its rotation axis, displacing the door from an outer partially closed position to an inner fully closed position. In other systems shown in German patent document 3,401,842 published Aug. 1, 1985 the bolt is mounted on a carriage fixed to a flexible element that is payed in and out to advance and retract it.
In all of these systems the end positions of the bolt are determined by the various transmission and drive elements that are under considerable stress in the fully closed position of the door and in the partially closed position when the bolt is struck by the latch fork. As these elements wear, the bolt can assume the wrong position, and the stress in and of itself adds to the wear of these parts.
It is therefore an object of the present invention to provide an improved power-closing bolt for a motor-vehicle door latch.
Another object is the provision of such an improved power-closing bolt for a motor-vehicle door latch which overcomes the above-given disadvantages, that is which is of simple construction and where the bolt is solidly held in its fully closed position without undue stress on the drive elements that move it from the partially closed to the fully closed position.
A power-closing bolt assembly for a motor-vehicle door latch has according to the invention a housing, a bolt pivotal in the housing about a pivot axis between a pair of angularly offset end positions, and interengaging bolt and housing abutments respectively on the bolt and on the housing bearing angularly of the pivot axis on each other in each of the end positions. A drive displaces the bolt between the end positions. The housing abutments are spaced apart relative to the pivot axis by more than 180xc2x0.
Thus with this system in the end positions there is positive angular engagement between the abutments that fix the bolt in these end positions. This eliminates the need to provide a nonreversing or binding type of drive, since the drive is not stressed in the end positions. The result is therefore a simple structure and much less stress applied to the drive.
The bolt according to the invention has a pair of end parts seated in the housing and centered on the pivot axis and a center part between the end parts and centered on a bolt axis parallel to but offset from the pivot axis. The housing abutment is a tab projecting radially of the pivot axis outward from one of end parts. The housing abutments are typically spaced in a standard side-door latch offset from a horizontal plane by 5xc2x0 to 10xc2x0 and the abutment tab on the bolt has a relatively narrow angular dimension so that in the end positions the horizontal forces normally bearing on the bolt will have a vector pressing the abutments together, not apart. Thus the radial forces exerted on the bolt as the fork is engaged over it during closing and by the seal once it is in the fully closed position will not tend to pivot the bolt, will tend to hold it in the end positions.
The housing according to the invention is generally U-shaped and has a pair of cheeks each formed centered on the pivot axis with a seat pivotally receiving a respective one of the end parts.
The power-closing bolt assembly wherein one of the end parts is formed with a socket. The drive has an output shaft fitted to the socket. The shaft and socket have complementarily interfitting formations that only allow the shaft and socket to fit together in one angular position relative to each other. The drive includes an electric motor and a transmission connected to the electric motor and having the output shaft. The drive further includes a mounting plate carrying the motor and transmission, traversed by the drive shaft, and fixed to the housing. The housing abutments are spaced apart by more than 180xc2x0 and are formed by angularly directed flanks of the housing and the bolt abutment is a radially outwardly projecting tab engageable n the end positions with the flanks.